If use 2-cell or morula stage embryos, should embryos be collected at 2-cell or morula stage or they can be collected at 1-cell stage then cultured in CO2 incubator for 1-2 more days before freezing?
We recommend to freeze fresh embryos, that is, if you will cryopreserve 2-cell stage embryos, collect them at 2-cell stage. The only reason is that, we don’t have (or don’t always have) the perfect in virto incubation conditions. If you think you can keep the quality of the embryos during in vitro incubation, you may do that. As a matter of fact, we tried to collect 1-cell stage embryos, and incubated them under our conditions, to morula stage, and then freezed them with our cryo solution. After thawing, we got very good survival rate. We would suggest you to do a test first, before you actually use this in vitro option.
